Martin
All I would say is don't panic on instruments as gyros is not that major a part from what i have seen and heard of many of the papers. I'm afraid I'm away from my notes so can't give the definitive list of errors but is it not just transport wander, earth rotaion and lat nut?
Surely they can't stop you sitting anyway - I thought exam applications had to be in by the 2 week cut off.
Make sure you are up to speed on the other stuff, especially IRS/INS and TCAS/GPWS.
SK